5.4 REFRACTION OF WAVES

CHAPTER 5
WAVES

5.3 REFRACTION OF WAVES

TEXT BOOK : PAGE 194 - 201

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

5.4 Refraction of Waves

(Pembiasan Gelombang)

The curve of the
wavefront is caused by

a phenomenon of
refraction of waves.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Refraction of waves is the change in
direction of propagation of waves caused
by the change in the velocity of waves when
the waves propagate from one medium to
another.

See, both waves
changing direction of

propagation

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Refraction of waves is the change in direction of propagation of waves caused
by the change in the velocity of waves when the waves propagate from one
medium to another.

See the wave changing
direction when travelling from
grey medium to blue medium

See the light wave changing
direction when moving from
dark medium to blue medium

What is medium? Cahaya berada di CHAPTER 5 WAVES
medium udara 5.4 REFRACTION OF WAVES
Cahaya berada di (air medium)
medium udara Medium is an
(air medium) surrounding
environment/region

Cahaya berada di
medium kaca
(glass medium)

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

shallow Different physical
medium
deep
(2 fizikal medium yg
berbeza)

Deeper and shallower
region is considered
different medium too.

Different density
(ketumpatan) is considered

different medium too.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Why different medium can cause the change
in direction of propagation of waves?

When you driving from a smooth area
to rocky region, direction would
changed too.

Change medium change direction of
movement.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

• Speed of water wave is influenced by depth of water.
• Speed of sound wave is influenced by density of air.
• Speed of light wave is influenced by optical density of medium

Running to/from sea, medium
changed, speed changed,
(And direction changed too if you are
not running in straight line (normally)
in to the sea)

Swim faster in deeper region.

Running from wider space to the
crowd (high density), speed and
direction changed too.`

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

From Activity 5.12, you will obtain the refraction of plane water wave.

Normal line

From deep water region
to shallow water region.

In deeper region, angle
between incident wave and

normal line α is bigger.

Ingat: lebih dalam (deeper) lebih luas,
lebih bebas, bergerak lebih cepat.

From deep water region CHAPTER 5 WAVES
to shallow water region. 5.4 REFRACTION OF WAVES

From shallow water region
to deep water region.

Deeper region, wider space,
wavelength longer, speed larger.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Effects of refraction on the characteristics of waves

Drawing Diagram of Refraction of Plane Water Waves CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Wavelength in shallow
region is shorter

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Bergerak ke kawasan lebih
dalam (lebih luas), kerbau pun

akan lari jauh sioknya kan

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Lets practise.

Angle between normal line Angle between normal line
and refracted wave is and refracted wave is
BIGGER. SMALLER.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

During the day, air that is closer to the surface CHAPTER 5 WAVES
of the earth is hotter. 5.4 REFRACTION OF WAVES

During the night, air that is closer to the
surface of the earth is colder.

Sound moves faster in hot air than in cold air. Sound is refracted towards the ground. This
So, sound is refracted away from the ground. causes the observer to hear sound more
Thus, cannot hear sound clearly during the clearly during the night.
daytime.

Away from the shoreline, the CHAPTER 5 WAVES
wavefront of the water is almost 5.4 REFRACTION OF WAVES
straight and parallel because water
waves move at a uniform speed. The cape (tanjong) is the shallower, while the bay
(teluk) deeper.

At cape, the speed of the water waves decreases
causing the wavelength to be shorter.

Wavefront of water approaching the bay moves at a
higher speed and the wavelength is longer. This
causes the wavefront to curve.

Refraction causes energy to converge towards the
cape.
Water wave energy diverges from the bay and
spread out to a wider region.
Thus, the amplitude of waves at bay is smaller than
at the cape.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Solving Problems Involving Refraction of Waves.
Refraction of waves is caused by the change in speed of waves.

Depth Wave speed Wavelength
changed changed changed

Frequency waves does
not changed !

Because frequency
determined on the
vibration of source.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Wavelength longer,
wave speed higher.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

Refraction.
Approaching beach, getting shallower, waves speed lower,
wavelength shorter, waves refracted.

CHAPTER 5 WAVES
5.4 REFRACTION OF WAVES

(a) v = f λ (b) v = f λ (d) Frequency same.
(30) = (10.0) λ v = (10.0) (1.5) Deeper region, longer
λ = 3 cm v = 15 cm s-1 wavelength.
Deeper region higher
waves speed.